Foldable display apparatus and method of manufacturing the same

ABSTRACT

Disclosed is a foldable display apparatus in which a crack prevention layer is disposed on a surface of a display panel. The crack prevention layer includes thin film pattern portions disposed along a folding axis of the foldable display apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority to and benefit of Korean PatentApplication No. 10-2017-0125406, filed on Sep. 27, 2017, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND 1. Field

One or more embodiments relate to a foldable display apparatus capableof being folded, and a method of manufacturing the same.

2. Description of the Related Art

Various types of display apparatuses such as flexible displayapparatuses, rollable display apparatuses, and foldable displayapparatuses have been developed. For example, a display apparatus suchas an organic light-emitting display apparatus may have a foldablestructure to be folded for convenience of portability.

However, when a foldable display apparatus keeps being folded andunfolded, stress is repeatedly applied around a folding axis, and cracksmay appear. When the cracks gradually propagate, the foldable displayapparatus may be damaged, and thus, the foldable display apparatus maynot properly operate.

SUMMARY

One or more embodiments include a foldable display apparatus that isimproved to restrict the appearance and propagation of cracks, and amethod of manufacturing the foldable display apparatus.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to one or more embodiments, a foldable display apparatusincludes: a display panel that is foldable along a folding axis; and acrack prevention layer disposed on a surface of the display panel,wherein the crack prevention layer includes a plurality of thin filmpattern portions disposed along the folding axis.

The plurality of thin film pattern portions may be disposed at apredetermined interval along the folding axis.

The plurality of thin film pattern portions may be spaced apart from oneanother.

The plurality of thin film pattern portions may be connected to form anintegrated structure.

The foldable display apparatus may further include a plurality ofauxiliary thin film pattern portions that is disposed at a secondpredetermined interval in a direction perpendicular to the plurality ofthin film pattern portions.

The plurality of thin film pattern portions may include any one of anorganic layer and an inorganic layer.

The plurality of thin film pattern portions may have a multi-layerstructure in which an organic layer and an inorganic layer are stacked.

The crack prevention layer may be on an outer surface of the displaypanel.

The crack prevention layer may be on inner and outer sides of thedisplay panel.

According to one or more embodiments, a method of manufacturing afoldable display apparatus includes: preparing a display panel that isfoldable along a folding axis; and forming a crack prevention layer on asurface of the display panel, wherein the crack prevention layerincludes a plurality of thin film pattern portions disposed along thefolding axis.

The plurality of thin film pattern portions may be disposed at apredetermined interval along the folding axis.

The plurality of thin film pattern portions may be spaced apart from oneanother.

The plurality of thin film pattern portions may be connected to form anintegrated structure.

The method may further include forming a plurality of auxiliary thinfilm pattern portions that is disposed at a second predeterminedinterval in a direction perpendicular to the plurality of thin filmpattern portions.

The plurality of thin film pattern portions may include any one of anorganic layer and an inorganic layer.

The plurality of thin film pattern portions may have a multi-layerstructure in which an organic layer and an inorganic layer are stacked.

The crack prevention layer may be on an outer surface of the displaypanel.

The crack prevention layer may be on inner and outer sides of thedisplay panel.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a front view illustrating an unfolded state of a foldabledisplay apparatus, according to an embodiment;

FIG. 2 is a front view illustrating a folded state of the foldabledisplay apparatus of FIG. 1;

FIG. 3A is a cross-sectional view illustrating an unfolded state of adisplay panel of the foldable display apparatus of FIG. 1;

FIG. 3B is a cross-sectional view illustrating a folded state of thedisplay panel of FIG. 3A;

FIG. 3C is a perspective view of the display panel of FIG. 3A;

FIGS. 3D to 3F are cross-sectional views of examples of thin filmpattern portions forming a crack prevention layer of the display panelof FIG. 3A;

FIGS. 4 to 6 are cross-sectional views of a modifiable example of acrack prevention layer of FIG. 3A;

FIG. 7A is a plan view of the display panel of FIG. 3A; and

FIG. 7B is a cross-sectional view illustrating a detailed structure of adisplay area of the display panel of FIG. 7A.

DETAILED DESCRIPTION

As the present disclosure allows for various changes and numerousembodiments, particular embodiments will be illustrated in the drawingsand described in detail in the written description. The attacheddrawings for illustrating embodiments of the present disclosure arereferred to gain a sufficient understanding of the present disclosure,the merits thereof, and the objectives accomplished by theimplementation of the present disclosure. The present disclosure may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein.

The present disclosure will now be described more fully with referenceto the accompanying drawings, in which exemplary embodiments of thedisclosure are shown. Like reference numerals in the drawings denotelike elements, and thus their description will be omitted.

As used herein, the singular forms “a”, “an,” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise.

It will be further understood that the terms “comprises” and/or“comprising” used herein specify the presence of stated features orcomponents, but do not preclude the presence or addition of one or moreother features or components.

It will be understood that when a layer, region, or component isreferred to as being “formed on” another layer, region, or component, itcan be directly or indirectly formed on the other layer, region, orcomponent. That is, for example, one or more intervening layers,regions, or components may be present.

Sizes of components in the drawings may be exaggerated for convenienceof explanation. In other words, since sizes and thicknesses ofcomponents in the drawings may be arbitrarily illustrated forconvenience of explanation, the following embodiments are not limitedthereto.

When a certain embodiment may be implemented differently, a specificprocess order may be performed differently from an order describedherein. For example, two consecutively described processes may beperformed substantially at the same time or performed in an orderopposite to the described order.

FIGS. 1 and 2 respectively illustrate an unfolded state and a foldedstate of a foldable display apparatus, according to an embodiment.

The foldable display apparatus includes a display panel 100 that may beflexibly bent. The display panel 100 may generally include a structure(refer to FIG. 7B) in which a thin film transistor and an emissionelement for producing an image, an encapsulation layer for covering andprotecting the thin film transistor and the emission element, and thelike are stacked on a flexible substrate. Since the flexible substrateis used instead of a rigid glass substrate, the display panel 100 may befolded and unfolded within a range of flexibility thereof. The displaypanel 100 may remain folded in the folded state, as illustrated in FIG.2.

As illustrated in FIGS. 1 and 2, the display panel 100 may be supportedby a case 300, and as the case 300 rotates, the display panel 100 may befolded or unfolded.

Compressive stress and tensile stress may be applied around a foldingaxis of the display panel 100 that is repeatedly bent and unbentwhenever the display panel 100 is folded and unfolded. That is, in thefolded state of FIG. 2, compressive stress is applied to an innersurface of the display panel 100 around the folding axis, and tensilestress is applied to an outer surface of the display panel 100. Herein,the outer surface of the display panel 100 corresponds to a surface ofthe display panel 100 that forms an outer side when the display panel100 is in the folded stated, whereas the inner surface of the displaypanel 100 faces each other when the display panel 100 is in the foldedposition in the cross-sectional view shown in FIG. 2. Referring to FIGS.1 and 2, the outer surface corresponds to a bottom surface of thedisplay panel 100, and the inner surface corresponds to an upper surfaceof the display panel 100. When stress keeps being applied in differentdirections, cracks may particularly appear in a portion of the displaypanel 100 where tensile stress is applied, and thus the cracks maypropagate.

In order to prevent cracks, in the present embodiment, a crackprevention layer 110 is formed on a folding axis F of the display panel100, as illustrated in FIGS. 3A to 3C. As illustrated in FIG. 3C, thecrack prevention layer 110 is formed by arranging multiple thin filmpattern portions that extend in a direction crossing the folding axis F,along the folding axis F at a predetermined interval. Although a foldingoperation and an unfolding operation are repeated, cracks may not easilyappear in the folding axis F due to the crack prevention layer 110, Evenif cracks appear, the crack prevention layer 110 that includes thin filmpatter portions arranged at a predetermined interval can preventpropagation of the cracks along the folding axis F through the displaypanel 100 as well as the crack prevention layer 110. The crackprevention layer 100 increases the resistance to the appearance andpropagation of the cracks.

The thin film pattern portion of the crack prevention layer 110 may be asingle organic layer 111, as illustrated in FIG. 3D, a single inorganiclayer 112, as illustrated in FIG. 3E, or a multilayer in which theorganic layer 111 and the inorganic layer 112 are stacked, asillustrated in FIG. 3F. The organic layer 111 may relieve stress byabsorbing fracture energy generated during the propagation of thecracks, and the inorganic layer 112 may function as a barrier thatprevents the propagation of the cracks. Thus, when the crack preventionlayer 110 is formed by properly combining the organic layer 111 with theinorganic layer 112, the appearance and propagation of the cracks may beeffectively prevented. In addition, since the entire folding axis is notcovered by the crack prevention layer 110, but the crack preventionlayer 110 include thin film portions arranged at a predeterminedinterval, the display panel 100 may be smoothly folded despite anincrease in a thickness of a peripheral area along the folding axis Fdue to the crack prevention layer 110. That is, although the crackprevention layer 110 is additionally formed, a folding operation is notdisturbed. When the thickness of the crack prevention layer 110excessively increases, the folding operation may be disturbed. Thus, itis advantageous to form the thin film pattern portions to have athickness of less than 5000 Å.

When the display panel 100 having the above structure is folded asillustrated in FIG. 3B, the greatest tensile stress is applied to anouter peripheral layer of the folding axis F, and thus the possibilitythat the cracks appear may increase. However, when the crack preventionlayer 110 is formed on the folding axis F, the appearance andpropagation of the cracks may be restricted.

A method of manufacturing a foldable display apparatus having the abovestructure will be described below, and an internal structure of thedisplay panel 100 will be briefly described first.

FIG. 7A schematically illustrates a planar structure of the displaypanel 100. The display panel 100 includes a display area DA where animage is displayed, and a non-display area NDA adjacent to the displayarea DA. The display area DA includes multiple pixel areas PA, and apixel that emits certain light is formed in each pixel area PA. As thepixels emit light in the display area DA, images are produced in thedisplay area DA.

The non-display area NDA may surround the display area DA and mayinclude driving units such as a scan driving unit (not illustrated) anda data driving unit (not illustrated) for transmitting signals to thepixels in the display area DA.

FIG. 7A illustrates that the non-display area NDA surrounds the displayarea DA, but one or more embodiments of the present disclosure are notlimited thereto. In another embodiment, the non-display area NDA may beon one side of the display area DA and may decrease an area, that is, adead area, where an image is not displayed.

As illustrated in FIG. 7B, a thin film transistor 121 and an organicemission element 122 are included in one pixel area PA of the displayarea DA. In a structure of the thin film transistor 121, an active layer121 f is disposed on a buffer layer 121 a that is disposed on a flexiblesubstrate 123 and has source and drain areas that are doped with N-typeor P-type impurities at high concentrations. The active layer 121 f mayinclude an oxide semiconductor. For example, the oxide semiconductor mayinclude an oxide selected from the group consisting of Groups 12, 13,and 14 metal elements such as zinc (Zn), indium (In), gallium (Ga), tin(Sn), cadmium (Cd), germanium (Ge), and hafnium (Hf), and a combinationthereof. For example, the active layer 121 f may includeG-I-Z-O[(In₂O₃)a(Ga₂O₃)b(ZnO)c] (where, a, b, and c are real numberssatisfying a≥0, b≥0, and c>0, respectively). A gate electrode 121 g isdisposed above the active layer 121 f with a gate insulating layer 121 btherebetween, and a source electrode 121 h and a drain electrode 121 iare disposed on the gate electrode 121 g. An interlayer insulating layer121 c is disposed between the gate electrode 121 g and the source anddrain electrodes 121 h and 121 i, and a passivation layer 121 d isdisposed between the source and drain electrodes 121 h and 121 i and ananode electrode 122 a of the organic emission element 122.

An insulating planarization layer 121 e including acryl, etc. isdisposed on the anode electrode 122 a. After an opening 122 d is formedin the insulating planarization layer 121 e, the organic emissionelement 122 is formed.

The organic emission element 122 displays image information by emittingred light, green light, or blue light according to a current flow, andis connected to the drain electrode 121 i of the thin film transistor121. The organic emission element 122 includes the anode electrode 122 aconnected to the drain electrode 121 i that supplies positive power tothe anode electrode 122 a; a cathode electrode 122 c covering the totalpixels and supplies negative power; and an emission layer 122 b that isdisposed between the anode electrode 122 a and the cathode electrode 122and emits light.

Adjacent to the emission layer 122 b, a Hole Injection Layer (HIL), aHole Transport Layer (HTL), an Electron Transport Layer (ETL), anElectron Injection Layer (EIL), etc. may be stacked.

The emission layer 122 b may be formed in each pixel in such a mannerthat pixels respectively emitting red, green, and blue lightcollectively form one unit pixel. Alternatively, regardless of locationsof the pixels, an emission layer may be commonly formed over the entirepixel area. In this case, the emission layer may be formed as layersincluding emission materials emitting, e.g., red, green, and blue light,are vertically stacked or combined with each other. If an emission layeremits white light, other combinations of colors may be made. Also, theemission layer may further include a color conversion layer or a colorfilter for converting the emitted white light into another color.

A thin film encapsulation layer (not illustrated), in which an organiclayer and an inorganic layer are alternately stacked, may be formed onthe cathode electrode 122 c.

Since the display panel 100 having the above structure may have aflexible structure, the display panel 100 may be bent or unbentaccording to the folding operation or unfolding operation as describedabove.

The foldable display apparatus having the above structure may bemanufactured as follows.

The display panel 100 that is foldable may be prepared.

As illustrated in FIG. 3C, the crack prevention layer 110 may be formedalong the folding axis F of the display panel 100. In this case, adeposition method using a mask may be used, and the thin film patternportions may be patterned as the single organic layer 111 of FIG. 3D,the single inorganic layer 112 of FIG. 3E, or the multilayer in whichthe organic layer 111 and the inorganic layer 112 are stacked asillustrated in FIG. 3F. Regardless of structure of the crack previsionlayer 110, the total thickness of the crack prevention layer 110 is keptto be less than 5000 Å.

The display panel 100, in which the crack prevention layer 110 is formedon the folding axis F, may be combined with the case 300 of FIG. 1.

When the foldable display apparatus is stored or transported, thefoldable display apparatus remains folded as illustrated in FIGS. 2 and3B, and accordingly stress is applied to the peripheral area of thefolding axis F of the display panel 100. However, since the crackprevention layer 110 including the thin film pattern portions is formedon the folding axis F, cracks may not easily appear even though thedisplay panel 100 is repeatedly folded or remains in a folded positionover an extended period of time. Although cracks may appear, the cracksmay not easily propagate due to the crack prevention layer 110, and thusa damage to the foldable display apparatus may be restricted.

When an image is viewed while the display apparatus is unfolded, thedisplay panel 100 is in the unfolded state by straightly unfolding thesame as illustrated in FIGS. 1 and 3A. Therefore, a user may view aplanar image on the display panel 100 that is straightly unfolded, andthe peripheral portion of the folding axis F is stably supported by thecrack prevention layer 110, and thus, the appearance and propagation ofthe cracks may be restricted.

In the present embodiment, the thin film pattern portions forming thecrack prevention layer 110 are spaced apart from one another, but asillustrated in FIG. 4, end portions of the thin film pattern portionsmay be connected in a zigzag manner and thus form an integratedstructure. That is, the structure of the crack prevention layer 110including the thin film pattern portions that cross the folding axis Fmay be basic, but the structure thereof may vary. For example, the endportions of the thin film pattern portions may be connected to orseparated from one another.

Also, as illustrated in FIG. 5, other than the thin film patternportions arranged at a predetermined interval along the folding axis F,the crack prevention layer 110 may further include auxiliary thin filmpattern portions 110 a that are arranged at a second predeterminedinterval in a direction perpendicular to the thin film pattern portions.That is, while the folding operation is repeatedly performed, stress mayalso be applied to the display panel 100 in a stretching direction (an Xdirection) by as much as stress applied to the folding axis F. When theauxiliary thin film pattern portions 110 a are formed, the auxiliarythin film pattern portions 110 a may prevent cracks from appearing andpropagating in the stretching direction.

Cracks may mostly appear in a portion where tensile stress is applied,and thus, according to the embodiments, the crack prevention layer 110is formed on an outer peripheral surface of the display panel 100 alongthe folding axis F. As illustrated in FIG. 6, the crack prevention layer110 may also be formed on an inner surface of the display panel 100where compressive stress is applied. That is, the crack prevention layer110 is formed on both sides of the display panel 100 to increase theresistance to cracks.

As described above, a foldable display apparatus may effectively preventcracks from appearing and propagating around a folding axis even thougha folding operation and an unfolding operation are repeatedly performed,and thus quality of a product may be stabilized.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present disclosure as definedby the following claims.

1. A foldable display apparatus comprising: a display panel that isfoldable along a folding axis; and a crack prevention layer disposed ona surface of the display panel, wherein the crack prevention layercomprises a plurality of thin film pattern portions disposed along thefolding axis.
 2. The foldable display apparatus of claim 1, wherein theplurality of thin film pattern portions is disposed at a predeterminedinterval along the folding axis.
 3. The foldable display apparatus ofclaim 2, wherein the plurality of thin film pattern portions is spacedapart from one another.
 4. The foldable display apparatus of claim 2,wherein the plurality of thin film pattern portions is connected to forman integrated structure.
 5. The foldable display apparatus of claim 2,further comprising a plurality of auxiliary thin film pattern portionsthat is disposed at a second predetermined interval in a directionperpendicular to the plurality of thin film pattern portions.
 6. Thefoldable display apparatus of claim 1, wherein the plurality of thinfilm pattern portions comprises any one of an organic layer and aninorganic layer.
 7. The foldable display apparatus of claim 1, whereinthe plurality of thin film pattern portions has a multi-layer structurein which an organic layer and an inorganic layer are stacked.
 8. Thefoldable display apparatus of claim 1, wherein the crack preventionlayer is disposed on an outer surface of the display panel.
 9. Thefoldable display apparatus of claim 1, wherein the crack preventionlayer is disposed on inner and outer sides of the display panel.
 10. Amethod of manufacturing a foldable display apparatus, the methodcomprising: preparing a display panel that is foldable along a foldingaxis; and forming a crack prevention layer on a surface of the displaypanel, wherein the crack prevention layer comprises a plurality of thinfilm pattern portions disposed along the folding axis.
 11. The method ofclaim 10, wherein the plurality of thin film pattern portions isdisposed at a predetermined interval along the folding axis.
 12. Themethod of claim 11, wherein the plurality of thin film pattern portionsis spaced apart from one another.
 13. The method of claim 11, whereinthe plurality of thin film pattern portions is connected to form anintegrated structure.
 14. The method of claim 11, further comprisingforming a plurality of auxiliary thin film pattern portions that isdisposed at a second predetermined interval in a direction perpendicularto the plurality of thin film pattern portions.
 15. The method of claim10, wherein the plurality of thin film pattern portions comprises anyone of an organic layer and an inorganic layer.
 16. The method of claim10, wherein the plurality of thin film pattern portions has amulti-layer structure in which an organic layer and an inorganic layerare stacked.
 17. The method of claim 10, wherein the crack preventionlayer is on an outer surface of the display panel.
 18. The method ofclaim 10, wherein the crack prevention layer is on inner and outer sidesof the display panel.
 19. The foldable display apparatus of claim 1,wherein the plurality of thin film pattern portions extend in adirection crossing the folding axis.
 20. The method of claim 10, whereinthe plurality of thin film pattern portions extend in a directioncrossing the folding axis.